Blends of cotton and polyester fibers are important textiles used in the manufacture of clothing and other textile products. As is well known, the dyes and process conditions used to color cotton are different than the dyes and processes used to dye polyester fibers.
Cotton fibers may be dyed using fiber reactive dyes of the vinyl sulfone, dichloroquinoxalone, halotriazine, and halopyrimidine types. The fiber reactive dyes may be applied to the fiber under alkaline conditions at a temperature ranging from about 40° to 110° C. in an aqueous solution containing an electrolyte which promotes exhausting the dye from the dye bath to the fiber. These dyes form a covalent chemical bond with the hydroxy groups of the cotton and exhibit excellent fastness properties. The fiber reactive dyes are also hydrophilic, have a high degree of affinity for cellulosic cotton fibers and are stable under alkaline pH conditions.
Polyester fibers are hydrophobic and generally may be dyed with disperse dyes which are also hydrophobic. The disperse dyes are sparingly soluble in water and typically may be dispersed in water with the aid of a dispersing agent, generally a surfactant in combination with other auxiliaries. Disperse dyes color the polyester fiber by diffusion into the fiber under the influence of heat and dyeing auxiliaries. Unfortunately, disperse dyes are generally not stable at higher pH and are normally applied at pH 5-7 at a temperature of 120°−140° C. Additionally, the disperse dye dispersion can be sensitive to electrolytes which tend to cause dispersion instability.
As will be appreciated, however, the polyester fibers comprising a cotton/polyester blend may have a slight affinity for fiber reactive dyes that are applied to the cotton, thereby giving rise to a wide variety of resultant color mixtures or patterns of the cotton/polyester blend whereby the reactive dyes may have very low affinity to the polyester thereby creating a distinct pattern by way of the dye and the fiber blended yarn.